Making ready cylindrical printing plate



Feb. 26, 1952 G. w. BUNGAY MAKING READY CYLINDRICAL PRINTING PLATE Filed Jan. 5, 1950 INVENTOR. G50/wf M U/vG/n/ BY 2% ,f/WIQMM /q ATTORNEYS.

Sl mQN nuova@ ...anbauen oonenanunnoonounon Patented Feb. 26, 1952 MAKING READYA CYLINDRICAL PRINTING PLATE George W. Bungay, New York, N. Y., assigner to Electrographic Corporation, New York, N. Y., a

corporation of Delaware Application January 5, 1950, Serial No. 137,010 4 Claims. (Cl. lill-401.3)

The present invention relates to a novel and improved process for making-ready letterpress printing plates for rotary printing.

Objects and advantages of theinvention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the processes, steps and combinations pointed out in the appended claims.

The invention consists of the novel steps, construction, processes, compositions and improvements herein shown and described.

Of the drawings:

Figure 1 is a schematic developed plan view of a typical and illustrative, arcuate letterpress or relief printing plate to be treated by the process of the present invention.

Figure 2 is a schematic developed plan view of an overlay for use in making-ready the plate of Figure 1.

Figure 3 is a similar view of the underlay which may be used in connection with the overlay of Figure 2.

Figure 4 is a schematic elevational View showing the bumping operation as carried out in accordance with the present invention; and

Figure 5 is a schematic side elevation of a printing plate treated in accordance with the present invention.

The present invention has for its object the provision of a novel and improved process for the accurate making-ready of curved or partcylindrical letterpress printing plates for use in rotary printing, particularly in the printing of high grade magazines and other periodicals. A further object is the provision of an improved process by which a curved plate may be accurately made ready with the portions for printing the solids or heavy tones substantially raised above the remainder of the surface of the plate. Still another object is the provision of a novel and improved process by which curved printing plates may be rapidly and accurately prepared for printing with a minimum of hand work on the plate.

Heretofore in the preparation of curved printing plates for rotary, letterpress printing, the making ready of the plates has been a relatively tedious and expensive operation, or else the making-ready has been carried out in a somewhat crude and inaccurate manner. Usually, the plate is made-ready after it has been clamped in position on the printing cylinder of the rotary printing press, and has been accomplished by production of a satisfactory underlay, or by reason of the lack of register between the underv lay and the face of the printing plate in case the underlay is formed from a proof vof the plate, as has usually been done.

In accordance with the present invention, the printing plate is preliminarily curved or is formed as an arcuate plate of the correct curvature. Such plates are usually electrotypes having a thickness of about one-quarter of an inch and about one-quarter circumference extent. Typically, such a plate would be about 111/2 by 151/2v inches, to print a page about 11 by l5 inches, and would be curved to t on a cylinder about 15 or 16 inches in diameter. Such plates may be halftone or line plates or a combination of halftone and line subjects to which is often added textual material. A plate of this general kind is trimmed to the desired size and the edges of the plate are bevelled or otherwise finished so that the plate may be secured on the printing cylinder in the usual manner. The plate is then positioned on .a conventional proof press and a proof is taken on suitable paper which is preferably a multi-ply laminated paper stock from which various layers may be individually removed in the desired areas so as to form an overlay.

Such a sheet of laminated stock generally comprises a heavy sheet of paper, often about- 0.010" thick, in which are secured a plurality of thinner layers of paper, each about 0.002 thick, which layers may be differently colored for convenience in separating the layers and for determining by inspection the depth of the removed portions of the paper. The proof impression is made on the uppermost thin sheet of paper and the several layers of paper are then removed as desired in accordance with the intensity of the tone of the impression. Thus, at those areas corresponding to the full tones or solids, two or three thicknesses of the thin paper would be removed, at the halftones of the plate only one thickness of the paper would be removed, while at the highlights none of the thin layers of paper would be removed. The removal of the layers of thin paper is easily accomplished by scribing around the various areas with a sharp knife so that one or more of the thin layers is cut through after which the one or two layers of thin paper are removed as desired.

I have found that this overlay may conveniently be made in accordance with the disclosure of the patent to Bishop No. 2,038,398 or 2,256,921, utilizing the make-ready stock there disclosed.

An underlay is also prepared which is to have thin layers of paper selectively removed from it, those areas corresponding to the highlight areas and a few number of layers in those areas corresponding to the halftone areas of the plate, while none of the thin layers of paper would be removed from the shadow or full-tone areas of the plate.

Such an underlay is not prepared by printing the plate in the conventional manner on the underlay sheet, but is prepared by rolling the paper Y over the inked plate while the plate is .simultaneously and proportionately advanced with respect to the underlay sheet, thereby producing an impression on the underlay sheet which is progressively shortened throughout its length with respect to the surface of the printing plate from which the impression was made. Thus for a quarter-cylindrical plate Vabout 0.250 thick having an cuter dimension of 11.5 by 15.5" and curved about its shorter dimension to iit a cylinder 15.5 in diameter, the overlay should be 11.5 by 15.5 while the underlay should be shortened by about 0.3 thereby giving anunderlay about 11.2" by 15.5", or with a ,shortening of about 0.027 per inch of arcuate length.

The underlay and overlay so formed are substantial complements of each other, one having its high areas corresponding .to the low areas of the other, and adapted to register radically with each` other when the two are positioned on the face and back respectively of the plate for which they. were made.

The overlay is then secured in register to the face of the plate and 4the underlay is secured to the back or concave side of the plate in radial register with the printing face of the plate. This securing of the .overlay and underlay may be made by means of any suitable temporary adhesive. Y

With the underlay and overlay in position on opposite sides of the printing plate, the printing plate is subjected to heavy radial pressure suicient to deform the plate and to push the solids or heavier tone portions of vthe plate outwardly, thereby raising them above 4the general surface of the printing face of the plate, this deformation being in accordance with the difference in thickness of the underlay and overlay at the different parts of the plate. The radial pressure may be as strong as desired so long `asno substantial crushing effect is produced on the finer halftone portions or small type areas of the plate, and is preferably accomplished by means of a pair of smooth surfaced Ycylindrical pressure rollers capable o f exerting several hundred pounds per lineal inch, one roller being driven while the other roller is an idler roller.

After this'bumping operation has 'been coml ness. After the overlay is removed, the plate is ready to be put on the press and printed.

It will be understood that the foregoing general description and the following detailed description as Well, are exemplary and explanatory of the invention, but are not restrictive thereof.

Referring now in detail to the present preferred and illustrative manner of carrying out the process of the present invention, as shown schematically in the accompanying drawings, Figure l shows the developed surface of a typical letterpress printing plate to be treated by the process of the present invention. As there shown, the plate 8 comprises nonprinting or highlight areas l0, halftone areas l2 and shadow or full tone areas i4, as well as heavy type matter I6. The full tone areas i4 and the heavy type matter I6 require heavier pressure in printing than the other areas of the plate and this heavier pressure is best obtained by raising these areas of the plate slightly above the general surface of the plate, while the halftone areas of the plate require to be raised only a lesser amount above the general surface of the plate, leaving the highlight areas at their original height. Y

Figure 2 shows the underlay 20 for use with the plate of Figure 1 and this underlay is of the same height as the plate 8 but is narrower than the plate, the difference in width being determined by the diameter of curvature of the plate, the .arcuate extent of the plate and the thickness of the plate. As shown in Figure 2, the underlay is formed of a plurality of thickness of paper, the bottommost sheet being relatively heavy while the two or more upper layers are thin and are preferably secured together by means of a Ytemporary adhesive over Atheir entire area. For a plate of the typical dimensions given, the plate 8 or the corresponding original from which the electrolype duplicate was prepared, is printed on the underlay sheet so that the underlay impression is progressively shortened throughout .its width, and this shortening may be 0.027 per inch `for the example given. The proofed underlay is then cut around the halftone and highlight or nonprinting areas 22 and one or more of the thin paper layers are removed from the underlay so as to leave the full tone areas 24 about 0.004" and the halitone areas 22 about 0.002 inch above the general level of the underlay. The underlay is then positioned on the concave side of the curved plate 8 and secured thereto in radial register with the design on the face of the printing plate.

The curved printing plate or the original plate fromwvhich the duplicate electrotype plate was prepared is then proofed on a sheet of paper suitable for making overlays and an overlay S0 is prepared.. In his overlay, as is shown in Figure 3, the areas 3K3 corresponding to the full tone areas I@ have two layers ci' thin paper iernovedwhile those areas 32 corresponding to the halftone areas |72 of the plate have one layer of the thin paper removed, and no paper is removed from the arcas 3,2 corresponding to the highlight or nen-printing areas I0 of the plate. Thus the underlay and overlay sheets are substantial complements of each other, except that the underlay is narrower than the overlay sheet.

Figure l diagrammatically illustrates the bumping operation with the underlay and overlay sheets temporarily secured to the under and outer surfaces of the plate respectively. The plate, with the underlay and overlay attached .to it is passed between the two smooth surfaced cylindrical pressure rollers 38, lili, one of which is a driven roller, while the other is preferably a non-driven or idler roller. These rollers are pressed togethe either, by yielding pressure or not, and exert a powerful pressure on the plate, underlay and overlay so as to deform the plate 8 in accordance With the varying heights of the underlay and overlay, the pressure being insufficient to cause any damage to the printing face of the plate.

After passage of the plate through the rollers I 38, 40, the plate preferably has the underlay removed from its back surface and the back surface may be shaved so as to reduce the plate to the desired finished thickness. After the plate has the overlay removed from it, it is ready to be clamped on the press and printed.

The invention in its broader aspects is not limited to the specific process and steps shown and described, but departures may be made therefrom within the scope of the accompanying claims Without departing from the principles of the invention and Without sacrificing its chief advantages.

What is claimed is:

1. The process' of making-ready an arcuate printing plate which comprises forming an over-` plate `while progressively shortening the impres.

sion with respect to the direction of curvature of the plate in the amount necessary to compensate for the shortening in the arcuate length of` the back of the plate as compared to the printing face, preparing an underlay from said sheet in accordance with the shortened impression, positioning the overlay in register on the face of the curved plate, positioning the underlay on the concave face of the plate and in radial register with the overlay, and subjecting the overlaid and underlaid plate to deforming pressure, finishing the concave back of the plate to render it cylindrical.

2. The process of making-ready an arcuate printing plate which comprises forming an overlay of the same size as the original for said plate, printing on an underlay sheet the design of said plate while progressively shortening the impression with respect to the direction of curvature of the plate in the amount necessary to compensate for the shortening in the arcuate length of the back of the plate as compared to the printing.

facepreparing an underlay from said sheet in accordance with the shortened impression, positioning the overlay in register on the face of the curved plate, positioning the underlay on the concave face of the vplate and in radial register With the overlay, subjecting the overlaid and underlaid plate to deforming pressure.

3. The process of making ready an arcuate printing plate which comprises forming an overlay of the same size as the original for the face of the arcuate plate, forming an underlay foreshortened in the amount necessary to compensate for the shortening in the arcuate length back of the plate as compared to the printing face for the concave back of the plate, positioning the overlay and underlay in radial register on the face and back of the arcuate plateJ respectively, subjecting the overlaid and underlaid plate to deforming radial pressure and removing the overlay to prepare the plate for printing.

4. A process as claimed in claim 3 in which the underlay is removed and the concave face of the plate is cylindrically finished.

GEORGE W. BUNGAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 903,342 Upham Nov. 10, 1908 906,586 Upham Dec. 15, 1908 908,267 Jacobson Dec. 29, 1908 988,763 Flower Apr. 4, 1911 1,005,619 Droitcour Oct. 10, 1911 1,128,351 Motley Feb. 16, 1915 1,152,393 Brown Sept. 7, 1915 1,537,461 Cates May 12, 1925 1,545,958 Greenway July 14, 1925 2,036,835 Sites Apr. 7, 1936 2,413,747 Chollar Jan. 7, 1947 

